Chantel warned her followers about the imposter, writing, "My iG is hacked everyone hold on I'll keep you guys update from snapchat (sic)."

The naked shot of Justin appeared alongside the caption: "I love you Justin."

It didn't fool many fans, who noted the image was one Justin had already shared on his own Instagram account, and in it he was wearing shorts.

After regaining control of her social media accounts and deleting the posts, Chantel posted a photo of herself sitting in her lawyer's office, holding up her middle finger. She captioned the defiant shot: "F**k u hacker."

The hack attack took place just days after Justin deleted his own Instagram account following a weekend war of words with Selena after she took aim at her former boyfriend for threatening to quit the photo-sharing site over mean comments some followers had posted about his new girlfriend, 17-year-old Sofia Richie.

He wrote: "I'm gonna make my Instagram private if you guys don't stop the hate this is getting out of hand, if you guys are really fans you wouldn't be so mean to people that I like."

That prompted his former girlfriend to respond: "If you can't handle the hate then stop posting pictures of your girlfriend lol (laugh out loud) - it should be special between you two only. Don't be mad at your fans. They love you and supported you before any one ever did."

Bieber has been caught in the buff twice this year by paparazzi snapping pictures of him baring all while out on vacation.